This invention relates to liquid hydrocarbon jet fuels and more particularly to azido additives to liquid hydrocarbon ramjet fuels.
In most liquid-fueled combustors such as the ramjet, the fuel is directly introduced into the upstream flow section of the combustion chamber in the form of sprays of droplets. These droplets subsequently mix with the external gas, heat up, gasify, combust, and thereby release heat to provide the propulsion energy. It is therefore obvious that the rates of gasification and mixing would closely affect the chemical heat release rate and consequently such important performance parameters as combustion efficiency and the tendency to exhibit combustion instability.
Attempts at enhancing the overall droplet gasification rate, and thereby reducing the combustor size, have emphasized the production of small droplets through spraying as well as increasing the gasification rates of individual droplets. Both approaches, however, have inherent difficulties. Concerning atomization, we note that there are three factors which place lower limits on the attainable droplet size. The first is that physically, droplets of infinitesimally small sizes cannot be produced through spraying. Secondly, exceedingly small droplets also lack sufficient inertia for penetration and therefore are undesirable from consideration of macro-scale mixing and homogeneity. Thus relying on spraying alone frequently cannot yield optimum gasification rate and mixture homogeneity. The third factor is that recent studies on the behavior of dense sprays have shown that even if very small droplets can indeed be produced, they will nevertheless collide and coalesce into much bigger droplets in the dense spray region next to the nozzle.
Concerning the droplet gasification rate, it is also well established that, for conventional hydrocarbon fuels, this rate is quite insensitive to changes in the system parameters in that while increases of tens of percents can be achieved through, say, convective augmentation or oxygen enrichment, increases by a factor of two or more are difficult to attain.